Resistance unit.



H. E. HEATH. RESISTANCE UNIT. APPLICATION rum) MAY 7 1907.

Patented Apr. 20, 1909.

Inventor Harry )3; Heath,

UNITED STATES BATENT; OFFICE.

HARRY E. HEATH, or LYNN, MASSACHUSETTS, Assrenon 'ro' GENERALELEGTRIOCOMPANY, A CORPORATION OF NEW YORK.

' RESISTANCE UNIT.-

Specification of Letters Patent.

Patented April 20, 1909.

Application filed May 7, 1907. sum No. 372,325.

citizen of the United States, residing at Lynn, county of Essex, Stateof Massachu setts, have invented certain newand useful Improvements inResistance. Units, of which the following is a specification.

This'invention relatesto resistance units for electric circuits and hasfor its obict the provision of a device of thischaracter which is simpleand cheap to construct and combines lightness and strength with a highdegree of efficiency and durability.

One of the objects of my invention is to provide a resistance unit whichshall have as large a surface and as small an amountof material aspossible.

in carrying out my invention 1 make the resistance unit in the form of atube formed of strips of material wound into a close spiral. This may bedone in various ways, two forms being shown and described in the accompanying specification.

in the drawings in which'I have illustrated my invention, Figure l is anelevation partly in section of one formof my invention; and Fig. 2 is asimilar view of another form without the connecting terminals.

in the construction of my resistance unit 1 take a strip of resistanceconducting ma.- terial, such as sheet iron or the like, and wind it intoa spiral with insulating material between the (Wm-lapping turns. "heinsulating; material is preferably of flexible and refractory material,such as asbestos. in the form shown in Fig. 1, the asbestos and themetal are inv strips of substantially equal width. The metal is lirstbent tothe l'orm shown in the drawing: in any desired manner, as forinstance by passing it through a die. The insulating material heredescribed being flexible will conform to the shape of' the metallicstrip without any previous treatment.- lhc two strips are arranged so asto overlap each other and are then wound into a closed spiral so thatthe metal turns will overlap each other \\ith the asbestos strip llbetween them. The strips may be olany dcsircd width so that the stripmay overlap itself any number of times, and in this way the sti ips forma corrugated llcxible tube, in which the turns are locked together bythe bends in the strips. The tube is then pro vided with cmincctingterminals 12 and 13,

manner.

and a rod 14 isypassed through the tube and terminals provided with nuts15 for securing I the whole in place. The tube may then be mountedbetween the brackets 16, if desired. In the form shown in Fig. 2, theflat'resistance conducting strip 17 and the lisbestos strip 18 are woundin the form of a closed spiral as shown. In this form the corrugationsare applied after the tube is formed. These corrugations'm'ay becircumferential and may thus be applied in a very simple Thecorrugations in this case, as well as in the form shown in'Fig. 1 notonly lock the spiral turns together but also lend strength to the tubesas a Whole. 7

It will be understood, of course, thatvarious modifications, both as tothe material and the method of construction, may be resorted to withoutdeparting from the spirit of my invention, the scope of which is setforth in the annexed claims. What I claim as new and desire to secure byLetters Patent of the United States, ,is,

1. 'A resistance tube comprising similarly shaped strips 'ofasbestos andconducting ma-' terial spirally wound so as. to overlap each other. i

2. -A resistance tube comprisinga resistance conductingstrip wound intoa closed spiral having a strip of asbestos of substantiallythesamelwidt'h between the overlapping turns.

3. A resistance tube comprising overlapping stripsof insulating'andconducting material wound into a closed spiral, the adja' cent edges ofsaid spiral being interlocked 4. A resistance tube comprisingoverlappingstrips of insulating and conducting ma-' terial wound into a closedspiral, the adjacent edges of said spiral being locked together bycm'rugati'ons.

5. A flexible resistance tube comprising a resistance conducting stripwound into a closed spiral, and a strip of asbestos wound between theoverlapping turns, the said tube beimg provided with corrugations forlocking; 100

the turns together. 7 In' witness whereof, I have hereunto set my handthis third dayof Way,19 07.

\ HARRY E. H'EA'IH. Witnesses: I

Join: A. MoMA'NUs, Jr., PHILIP F. HARRINGTON.

